SW: TOR - Revenue "More Than Doubled" Since Going Free-to-play

I played it up to Level 11 as a smuggler. Does this this game become challenging later? - 'til now it is boring as hell, nearly no tactics needed.

The class story and quests stay easy as pie so that even the more casual gamers can finish their class stories.
There are some challenging side quests though and you can always team up and do some HEROIC+2 or HEROIC+4 or a Flashpoint if you need something to stay awake. Some of the HEROIC+2 can be solo'd if you use your skills to their full potential and that is pretty challenging, too.

Once you're level 50 (or 55 now after ROTH), you can start the real grind (everything up to level 50/55 is just foreplay ) and really get into Flashpoints and Operations. The Flashpoints can be (and should be!) played in Hard Mode and there are a number of Flashpoints where hard mode definitely works as advertised.
Ops are supposed to be even more challenging but due to the lack of a guild (and lack of time), I have personally never done any Ops.
I actually burnt out during the "run dailies and grind Flashpoints for gear" phase. I think I'll play through ROTH just for the story and to get my character to level 55 but then I may quit this game for good…

Towards the last 20 levels, you will have a really hard time soloing even single content (depending on class tho'). My Marauder is twinked, and I ain't a bad player, but I get swatted often if I don't pull my healer companion. Sometimes even if I do.